Hydrocarbon fluids, such as oil and natural gas, are commonly obtained from subterranean geologic formations by drilling a well that penetrates a hydrocarbon-bearing formation. Once a wellbore has been drilled, the well must be completed before the fluids can be produced from the well. A typical completion involves the design, selection, and installation of equipment and materials in or around the wellbore for conveying, pumping, or controlling the production or injection of fluids therein. After the well has been completed, production of the hydrocarbon fluids can begin.
When the hydrocarbon fluid is eventually produced from the subterranean formation, the fluid typically contains particulates, such as sand. Problems caused by sand production can significantly increase operational and maintenance expenses and can potentially lead to a total loss of the well. To control sand production, one technique commonly employed involves the installation of a gravel packing system in the wellbore where the well fluid is routed through a downhole filter formed from gravel that surrounds a sand screen.
More specifically, the sand screen is a cylindrical mesh apparatus that is disposed around the production tubular and arranged generally concentric with the borehole where well fluid is produced. Gravel is packed between the annulus formed between the formation and the sand screen. The well fluid produced from the hydrocarbon formation passes through the gravel, enters the sand screen and is eventually communicated uphole via the production tubular. The gravel surrounding the sand screen is typically introduced into the well in the form of a slurry comprising a mixture of a carrier fluid and gravel. The gravel packing system directs the slurry around the sand screen so that when the fluid in the slurry disperses, the gravel remains seated around the sand screen.
In some applications, such as when relatively long formations are being gravel-packed, zonal isolation is undertaken to define and isolate multiple zones along the length of the wellbore. Conventionally, zonal isolation is accomplished using manmade isolation devices, such as cup packers, which can be bypassed for gravel packing using shunt tubes. However, the combination of shunt tubes and cup-type isolation packers often fails to provide sufficient isolation between adjacent zones.
There is a need, therefore, for improved tools and methods for providing an adequate bather and isolating multiple hydrocarbon zones.